With Dr. Laqueur it is planned to continue the study of tumor production by cycasin and cycasin related compounds. We hope to determine which compounds are formed by bacterial enzymes and which may be formed by enzymes within the tissues of the host animal. It is planned to determine the effective dose, and the time required for formation and the location of tumors caused by the various compounds. The ultimate objective will then be to determine the chemical structure of the actual carcinogen causing the cycasin induced tumors, and the mechanisms by which their influences are exerted. With Dr. Smith we plan to continue the study of the interrelationships between vitamin A and the trace element zinc. It is hoped to determine whether zinc is necessary for the actual utilization of vitamin A as well as for its mobilization from the liver and subsequent transport. Attempts will be made to identify the mechanisms by which zinc exerts its influence. We also hope to determine why lack of growth appears to inhibit the ability of zinc to influence the utilization of vitamin A.